TRY IT -- you have nothing to loose - it will cost you nothing except the non contact thermometer that you may [ or should ] have anyway

if the warm side bath gains too much energy or warmth - you can simply shield or insulate some of the radiation /baseboard [don't block the flow - block the radiation of energy into the room] with a rug or something creative that will pose no fire / trip / or other safety hazard - then keep balancing

BTW -- this isn't exactly the best time of season to test and correct because the outdoor temperatures do not give the load much of a challenge - so tweek slightly

or simply wait till next December and go for it

oh -- just one thing more - via that diagram you will be choking flow on the WRONG side of the circulator that is piped [ apparently ] to pump [sort of] at the point of no pressure change - don't let that blow you away - its just a simple way to support the advice from above - BUT don't choke too much and defiantly don't' choke both sides in of this diagram at the same time - if you have been reading you will immediately know why and this advice is redundant - just trying to help avoid a mistake.

If one were to use a "direct return" piping system, where each "circuit" operated independently (each a different zone with its own circulator, thermostat etc..), Would "balancing" one zone vs. another be unnecessary (all are dissimilar btu requirements)? Am I correct in my understanding that Balancing a system is to achieve even heat in each part of a single zone (so that you do not have some hot rooms and some cold)?

Below is an example of what I'm talking about, Nothing is to scale. I think I have made notes of anything that may raise questions.

[quote="Boots"]If one were to use a "direct return" piping system, where each "circuit" operated independently (each a different zone with its own circulator, thermostat etc..), Would "balancing" one zone vs. another be unnecessary (all are dissimilar btu requirements)?quote]IF each of the zones are exactly the same in pipe size - length of runs - radiation installed - and each load served is exactly the same = no do you qualify on all that?

[quote="Boots"]Am I correct in my understanding that Balancing a system is to achieve even heat in each part of a single zone (so that you do not have some hot rooms and some cold)? quote]

Room [ hot and cold] is [first] controlled by the zone thermostat --- then if the zone has some / all / or any of the differences I mentioned above - well sometimes / usually / often --- those differences can be compensated for.

if the system is designed correctly from the start then each zone [and area in each zone] has the correct radiation and correct energy flow to support it - This is varied by the outdoor reset control to adjust for seasonal/ daily load differences - its balanced because it was designed to be.

The correct place to do the radiation balancing is on the paper you engineered and designed from calculations, not a guess. BUT often the lowest bidder didn't have a sharp pencil - he usually wasn't even the sharpest tool in the shed!